A 2,000-mile-long wall separating the United States and Mexico across some of the most inhospitable terrain in the United States would be a monumental project, despite Donald Trump’s assurance that it would be easy. (Here's what he said when asked how he would build the wall: "Very easy. I’m a builder. That’s easy." Easy to say, anyway.)

But I had been wondering whether he envisioned the proposed wall at the border with Mexico as being made of concrete—the logical choice, I think. Trump has used concrete in the past, such as at Chicago’s Trump Tower which is the tallest reinforced concrete building in the United States.

Then I came across an amusing exploration of the topic by a structural engineer. He concludes that the best approach to build the wall would be precast posts and panels that would require 12.6 million cubic yards of concrete and about 5 billion pounds of reinforcing steel.

I was thinking more about a slipformed wall, myself. If the wall was 20 feet high above grade and 6 feet below grade to prevent easy tunneling beneath it would have to be at least 8 inches thick. For a 2,000-mile-long wall, that would require 141 million cubic feet, or 5.2 million cubic yards of concrete not including what would go into the foundations. With that in mind, building the wall is not impossible, certainly, but it would suck up a lot of the nation’s cement supply and would require a lot of workers, most likely Mexicans.

It would certainly be an amazing project with many unknowns and would require a lot of innovation. Sounds like fun! I guess I’ll have to vote for Trump after all.

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